Implement a class Employee that support methods: name(firstname): Takes one's first name as input
rate(payrate): Takes one's hourly pay rate as input
changeRate(newpayrate): Takes the new pay rate as input and changes the employee's pay rate to the new hourly rate
pay(hours): Takes the number of hours worked as input and returns total payment (i. e. one's pay rate * total hours)
>>> e1 = Employee()
>>> e1.name('Jeff')
>>> e1.rate(10)
>>> e1.changeRate(20)
>>> e1.pay(20)
400
'''